The present invention relates to a crash helmet with a spherical cap part.
Crash helmets are used predominantly by motorcycle riders who are trying to protect their heads from injury in the case of an accident. For a considerable period of time, crash helmets have been made mainly from approximately spherical or elongated oval shaped synthetic resin cap parts, which form the outer, impact and shock resistant shell of the crash helmet. The cap part is equipped with a soft inner lining which is fitted to the head of the wearer. In the case of an integral helmet, the cap part includes an integrally formed chin strap to protect the chin area of the wearer. Above the chin strap, the cap is provided with a sight opening which may be covered with a transparent visor.
An integral helmet of this type must have certain minimum dimensions in view of the stringent requirements relating to comfort and impact absorbing properties of the inner lining. Because of its relatively large size, the crash helmet therefore represents an object which offers an appreciable resistance to air, particularly at higher speeds, and consequently exerts a not inconsiderable force on the wearer of the helmet, which must be absorbed by his neck muscles. As a result, during extensive trips at a high speed, the wearer suffers certain fatigue phenomena caused by the stress on the muscles of the neck.
In order to keep the air resistance forces applied to the helmet to a minimum, it has been attempted to provide crash helmets with aerodynamically favorable shapes. In order to obtain a laminar flow with a minimum of friction on the surface of the helmet, the surface of the helmet is made as smooth as possible, which is easily accomplished, in particular with synthetic resin crash helmets.
The possibility of altering the approximately spherical configuration of the cap part to improve its aerodynamics is limited, on the one hand by the shape of the head of the wearer and, on the other, by the necessity of allowing the wearer to turn his head while travelling, to observe the flow of traffic.